This invention relates to a thyristor valve adapted to be used in a power line system such as a high voltage DC power transmission system and an AC power system interconnecting power lines of different frequencies, and more particularly to an enclosed thyristor valve whose maintenance and inspection are substantially simplified.
According to a remarkable progress in recent years in the field of semiconductor technology, there has been developed a thyristor element which is operable at high voltage and heavy current and which is directly fired by a light signal. Thyristor valves or thyristor switching devices utilizing the aforementioned thyristor elements have also been developed and the capacities thereof have been increased constantly. According to the increase in voltage and current, a cooling device for the thyristor valves which is simple in construction and of a high efficiency is urgently required.
In order to satisfy such requirement, an enclosed type construction wherein the thyristor elements and others are enclosed in a tank filled with an insulating gas such as SF.sub.6 gas and cooled by a coolant such as oil, water, flon and the like has been heretofore proposed.
Although a thyristor valve of the above described construction is found to be operable satisfactorily, the inspection and maintenance thereof become extremely difficult. Ordinarily, a thyristor valve contains tens of thousands of parts, some of which must be replaced periodically during several years of usage. When the parts are replaced or when the thyristor valve has a trouble, the parts must be pulled out of the tank for the purpose of inspection and maintenance, and the fact how the time and labor required for the inspection and maintenance can be reduced constitutes a problem which must be solved urgently.